Absorbent article with breathable backsheet comprising one layer with improved capillary apertures

ABSTRACT

The present invention relates to breathable absorbent articles like baby diapers, adult incontinence articles and in particular to sanitary napkins or pantiliners. According to the present invention the articles are provided with an apertured backsheet for breathability. At least one of the breathable layers of the backsheet comprises a resilient, three dimensional web which consists of a liquid impervious polymeric film having apertures. The apertures form capillaries which are designed such that the backsheet provides an increased barrier to liquid passage out of the article and maintains water vapor permeability when the web is exposed to compressive pressure.

FIELD OF THE INVENTION

The present invention relates to breathable absorbent articles like babydiapers, adult incontinence articles and in particular to sanitarynapkins or pantiliners. According to the present invention the articlesare provided with an apertured backsheet for breathability. At least oneof the breathable layers of the backsheet comprises a resilient, threedimensional web which consists of a liquid impervious polymeric filmhaving apertures. The apertures form capillaries which are designed suchthat the backsheet provides an increased barrier to liquid passage outof the article and maintains water vapour permeability when the web isexposed to compressive pressure.

BACKGROUND OF THE INVENTION

The primary consumer needs which underlie development in the absorbentarticle field, in particular sanitary napkins, catamenials, orpantiliners is the provision of products providing both a highprotection and comfort level.

One means for providing consumer comfort benefits in absorbent articlesis by the provision of breathable products. Breathability has typicallyconcentrated on the incorporation of so called ‘breathable backsheets’in the absorbent articles. Commonly utilised breathable backsheets aremicroporous films and apertured formed films having directional fluidtransfer as disclosed in for example U.S. Pat. No. 4,591,523. Both thesetypes of breathable backsheets are vapour permeable allowing gaseousexchange with the environment. This thereby allows for the evaporationof a portion of the fluid stored in the core and increases thecirculation of air within the absorbent article. The latter isparticularly beneficial as it reduces the sticky feeling experienced bymany wearers during use, commonly associated with the presence of anapertured formed film or film like topsheet.

A drawback associated with the use of breathable backsheets in absorbentarticles is the negative effect on the protection level performance byleakage, known as wet through, onto the users garment. Although,breathable backsheets in principle only allow the transfer of materialsin the gaseous state, physical mechanisms such as extrusion, diffusionand capillary action may still occur and result in the transfer of thefluids from the absorbent core through the backsheet and onto the usersgarments. In particular, these mechanisms become more dominant if thebacksheet is compressed e.g. during physical exertion, especially forheavy discharge loads or over extended periods of time. Thus, whilst theincorporation of breathable backsheets in absorbent articles is highlydesirable from a comfort standpoint, since the primary role of abacksheet still remains the prevention of liquid leakage, conventionalbreathable backsheets have not always been satisfactorily incorporatedinto products.

The problem of wet through onto users garments due to the incorporationof such breathable backsheets in absorbent articles has indeed also beenrecognized in the art. Attempts to solve the problem have mainly residedin the use of multiple layer backsheets such as those illustrated inU.S. Pat. No. 431,216. Similarly European patent application no. 710 471discloses a breathable backsheet comprising an outer layer of a gaspermeable, hydrophobic, polymeric fibrous fabric and an inner layercomprising an apertured formed film having directional fluid transport.The backsheet construction preferably has no liquid transport/wetthrough under certain specified test conditions. Also European patentapplication no. 710 472 discloses a breathable backsheet consisting ofat least two breathable layers which are unattached to one another overthe core area. The backsheet construction preferably has no liquidtransport/wet through under certain specified test conditions.

U.S. Pat. No. 4,713,068 discloses a breathable clothlike barrier for useas an outer cover for absorbent articles. The barrier comprises at least2 layers, a first layer having a specified basis weight, fiber diameterand pore size and a second layer comprising a continuous film ofpoly(vinyl alcohol) having a specified thickness. The barrier also has aspecified water vapour transmission rate and level of impermeability.

However, none of the above proposed solutions have been able to providea fully satisfactory solution to the problem of wet through preventionunder all conditions, especially when the article incl. the breathablebacksheet is compressed.

U.S. Pat. No. 5,591,510 as well as WO 97/03118 and WO 97/03795 disclosean apertured film layer having capillaries which are disposed at anangle relative to the plane of the film, which films are referred to asslanted capillary films. This film structure is provided as aimprovement for incorporation into clothing and garments which arebreathable, yet non transmitting liquids toward the wearer of suchgarments. Also the use of such slanted capillary films is indicated inthe context of absorbent articles but as a topsheet, particularly inFIG. 16 of U.S. Pat. No. 5,591,510 the combination of such slantedcapillary films together with an absorbent material is disclosed,however not in the context of disposable absorbent articles according tothe present invention.

Another problem which occurs when the article is put to use and exposedto compressive pressure or high discharge loadings is that the effectivebreathability is drastically reduced. For example when liquid hascontacted a microporous film the water vapour transmission iseffectively eliminated. When considering apertured capillary films ofthe prior art the water vapour transport is also drastically reducedwhen they are exposed to pressure but remains at a low level.

It is hence an objective of the present invention to provide absorbentarticles which have a breathable backsheet designed such that theyprovide an increased barrier to liquid passage when exposed to pressurewhile at the same time the water vapour permeability, i.e. what isconventionally understood as breathability, is less reduced than thewater vapour permeability of conventional apertured capillary films(provided they are not made from a water vapour permeable material).

It is another objective of the present invention to provide a disposableabsorbent article having and maintaining improved breathability whilehaving and maintaining an acceptable level of protection, i.e. beingexceptionally leakage resistant, in particular when the article isexposed to pressure.

SUMMARY OF THE INVENTION

The present invention relates to breathable disposable absorbentarticles of a layered construction such as baby diapers, adultincontinence articles and in particular sanitary napkins or pantyliners. Also articles such as underarm sweat pads, breast pads, or shirtscholars may benefit from the present invention. Typically such articlesare of layered construction with each layer or group of layers having agarment facing surface which is oriented to face in the direction of agarment during use of the article and a wearer facing surface facing inthe opposite direction. Typically such articles comprise a liquidpervious topsheet forming the wearer facing surface of the article, anabsorbent core and a breathable backsheet forming the garment facingsurface of the article. The absorbent core is interposed between thetopsheet and the backsheet. However, according to the present inventionthe absorbent core may provide the wearer facing surface of the articlesuch that this surface of the core also provides the functions of thetopsheet.

The breathable backsheet is located on the garment facing surface of theabsorbent core and comprises at least a first backsheet layer. It canfurther comprise additional layers such as a second backsheet layer. Thefirst backsheet layer is positioned between the garment facing surfaceof the absorbent core. In order to provide the article withbreathability all backsheet layers are at least water vapor permeable,preferably air permeable. The first backsheet layer comprises aresilient three dimensional web, which consists of a liquid imperviouspolymeric film which film has apertures. The apertures form capillarieswhich have side walls which extend away from the wearer facing surfaceof the film providing the web with three dimensionality. The capillarieshave a first opening in the garment facing surface of the film and asecond opening at the end of the capillaries spaced apart from thewearer facing surface of the film. Preferably the capillaries extendaway from the wearer facing surface of the film at an angle which isless than 90° in respect to the plane of the film.

In co-pending patent applications based on priority document EP 98101867and EP 98101868 a combination between a slanted capillary filmbacksheet, an optional second of the film. The center axis is defined asthe line which connects the center point of the first opening of acapillary and the center point of the second opening of a capillary.

For some embodiments it is also possible that the first opening of atleast some of the capillaries is larger than the second opening of therespective capillary such that the capillaries themselves form coneswhich have an increase in capillary action in a direction towards theabsorbent core. In yet another embodiment according to the presentinvention the capillaries are curved towards or appear bent towards theplane of the film. In an alternative or in addition thereto thecapillaries have a first and a second portion which are different indirection, form, shape, size or combinations thereof.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 shows a cross-sectional view of an absorbent article comprisingall usual elements of such articles including a preferred embodiment ofthe breathable backsheet with a second layer according to the presentinvention.

FIGS. 2-4 show particular preferred embodiments of the slantedcapillaries used for the three dimensional web of in the breathablebacksheet according to the present invention.

FIGS. 5 and 6 are a top plan view and cross section of the compressionplates used in the modified water transmission resistance test.

DETAILED DESCRIPTION OF THE INVENTION

The present invention relates to absorbent disposable articles such assanitary napkins, panty liners, incontinence products, sweatpads, breastpads, and baby diapers. Typically such products comprise the elements ofa liquid pervious topsheet, a backsheet and an absorbent coreintermediate said topsheet and said backsheet. According to the presentinvention the topsheet, backsheet and core may be selected from any ofthe known types of these components provided that they meet the desiredcomfort and protection performance requirements and conditions notedbelow and in the appended claims.

In general, the topsheet—if present—should have good liquid retention tomaintain a dry surface and thereby keep the skin of the wearer dry; theabsorbent core needs to layer in the backsheet and a film topsheet havebeen disclosed. The backsheet construction in these disclosures doesprovide a major step beyond the here to forth known three dimensionalformed film aperture designs or breathable backsheets. However it hasnow been found that a further step in improving the leakage resistanceof absorbent articles and maintenance of their airpermeability can beachieved by the designs according to the present invention. The threedimensional web of the first backsheet layer has a liquid watertransport resistance (WTR) in a direction from the second openingtowards the first opening of the capillaries in the web towards theoutside which is measured by a modified DIN53886 test for WTR. The webalso has a water vapour permeability (WVP) in the same direction as theWTR and which can be measured by a modified ASTM E 96-80 test of WVT.

According to the present invention it has surprisingly been found thatthe WTR, i.e. the liquid water transport resistance increases for thefilms according to the present invention by at least 50%, preferably byat least 65%, most preferably by at least 75% or more, when comparingthe rate at ambient pressure (i.e. no compression) versus a compressionof 6865 Pa above ambient. Under the same pressure differential the watervapour permeation, despite an increased water transport resistance isnot completely eliminated but reduces by less than 80%, preferably byless than 60% of the WVP at ambient pressure (i.e. without compression).

It is in itself surprising that the webs according to the presentinvention have an increased resistance to liquid permeation through themwhen exposing the web to an increased pressure but combining this withthe ability to maintain water vapour transport and preferablyairpermeability is a considerable surprise to those skilled in the art.

According to the present invention the capillaries are preferablyidentical and homogeneously distributed across the film at a spacingwhich does insure the above mentioned limited WVP reduction by less than80% and preferably by even less than 60% (again when comparing betweenambient and the compression under a pressure of 6865 Pa).

Preferably a center axis of each capillary forms an angle between 85°and 20°, more preferably between 65° and 25° and most preferably between55° and 30° with the plane provide enough absorbent capacity and allowthe flow of vapour and/or air through it and the backsheet shouldprevent wet through (liquid permeability) to retain the absorbed fluidwhile being sufficiently breathable. Furthermore, the individualelements are joined, preferably using techniques such that the finalproduct has the desired comfort and performance level.

In the following description of the invention the surface facing in thedirection of the wearer is called wearer facing surface. In the drawingsthis direction is indicated by arrow 20. Further the surface facing inthe direction of the garment is called garment facing surface and in thedrawings this direction is indicated by arrow 21.

Absorbent Article Components

The Topsheet

According to the present invention the absorbent article usuallycomprises a topsheet. The topsheets suitable for use herein may be anytopsheet known in the art. In FIG. 1 the topsheet is indicated withreference numeral 30.

The topsheets for use herein may comprise a single layer or amultiplicity of layers. In a preferred embodiment the topsheet comprisesa first layer which provides the user facing surface of the topsheet anda second layer between the first layer and the absorbent structure/core.In addition another layer on the wearer facing surface of the firstlayer but only extending in the central zone or in parts of theperipheral zone of the article can be desirable to provide extrasoftness or extra liquid handling/retaining abilities (this design isusually referred to as “hybrid topsheet”). The topsheet typicallyextends across the whole of the absorbent structure and can extend intoand form part of or all of the preferred sideflaps, side wrappingelements or wings.

The topsheet as a whole and hence each layer individually needs to becompliant, soft feeling, and non-irritating to the wearer's skin. Italso can have elastic characteristics allowing it to be stretched in oneor two directions. As used herein the topsheet hence refers to any layeror combination of layers whose principle function is the acquisition andtransport of fluid from the wearer towards the absorbent core andcontainment of the absorbent core. In addition the topsheet of thepresent invention should have a high vapour permeability preferably alsoa high air permeability.

According to the present invention the topsheet may be formed from anyof the materials available for this purpose and known in the art, suchas wovens, non wovens, films or combinations thereof. In a preferredembodiment of the present invention at least one of the layers of thetopsheet comprises a liquid permeable apertured polymeric film.Preferably, the wearer facing and contacting layer is provided by a filmmaterial having apertures which are provided to facilitate liquidtransport from the wearer facing surface towards the absorbentstructure, as detailed for example in U.S. Pat. Nos. 3,929,135,4,151,240, 4,319,868, 4,324,426, 4,343,314 and 4,591,523. However, evennon-woven or woven substrates can be apertured to improve their functionof liquid acquisition.

Absorbent Core

According to the present invention the absorbent cores suitable for useherein may be selected from any of the absorbent cores or core systemknown in the art. As used herein the term absorbent core refers to anymaterial or multiple material layers whose primary function is toabsorb, store and distribute fluid. In FIG. 1 the absorbent structure isshown to comprise 3 layers 40, 42, and 44.

The absorbent core of the present invention should have a high vapourpermeability preferably also a high air permeability. The absorbent corepreferably has a caliper or thickness of less than 12 mm, preferablyless than 8 mm, more preferably less than 5 mm, most preferably from 4mm to 2 mm.

According to the present invention, the absorbent core can include thefollowing components: (a) an optional primary fluid distribution layerpreferably together with a secondary optional fluid distribution layer;(b) a fluid storage layer; (c) an optional fibrous (“dusting”) layerunderlying the storage layer; and (d) other optional components.

Primary/Secondary Fluid Distribution Layer

One optional component of the absorbent core according to the presentinvention, indicated as layer 40 in FIG. 1, is a primary fluiddistribution layer and a secondary fluid distribution layer. The primarydistribution layer typically underlies the topsheet and is in fluidcommunication therewith. The topsheet transfers the acquired fluid tothis primary distribution layer for ultimate distribution to the storagelayer. This transfer of fluid through the primary distribution layeroccurs not only in the thickness, but also along the length and widthdirections of the absorbent product. The also optional but preferredsecondary distribution layer typically underlies the primarydistribution layer and is in fluid communication therewith. The purposeof this secondary distribution layer is to readily acquire fluid fromthe primary distribution layer and transfer it rapidly to the underlyingstorage layer. This helps the fluid capacity of the underlying storagelayer to be fully utilised. The fluid distribution layers can becomprised of any material typical for such distribution layers.

b Fluid Storage Layer

Positioned in fluid communication with, and typically underlying theprimary or secondary distribution layers, is a fluid storage layer (42).The fluid storage layer can comprise any usual absorbent material orcombinations thereof. It preferably comprises absorbent gellingmaterials usually referred to as “hydrogel”, “superabsorbent”,hydrocolloid” materials in combination with suitable carriers, which areindicated as particles (43) in FIG. 1.

The absorbent gelling materials are capable of absorbing largequantities of aqueous body fluids, and are further capable of retainingsuch absorbed fluids under moderate pressures. The absorbent gellingmaterials can be dispersed homogeneously or non-homogeneously in asuitable carrier. The suitable carriers, provided they are absorbent assuch, can also be used alone.

Suitable absorbent gelling materials for use herein will most oftencomprise particles of a substantially water-insoluble, slightlycross-linked, partially neutralised, polymeric gelling material. Thismaterial forms a hydrogel upon contact with water Such polymer materialscan be prepared from polymerizable, unsaturated, acid-containingmonomers which are well known in the art.

Suitable carriers include materials which are conventionally utilised inabsorbent structures such as natural, modified or synthetic fibers,particularly modified or non-modified cellulose fibers, in the form offluff and/or tissues. Suitable carriers can be used together with theabsorbent gelling material, however, they can also be used alone or incombinations. Most preferred are tissue or tissue laminates in thecontext of sanitary napkins and panty liners.

An embodiment of the absorbent structure made according to the presentinvention comprises a double layer tissue laminate. These layers can bejoined to each other for example by adhesive or melting a polymericpowder binder (e.g. PE powder), by mechanical interlocking, or byhydrogen bridge bends. Absorbent gelling material or other optionalmaterial can be comprised between the layers.

Modified cellulose fibers such as the stiffened cellulose fibers canalso be used. Synthetic fibers can also be used and include those madeof cellulose acetate, polyvinyl fluoride, polyvinylidene chloride,acrylics (such as Orlon), polyvinyl acetate, non-soluble polyvinylalcohol, polyethylene, polypropylene, polyamides (such as nylon),polyesters, bicomponent fibers, tricomponent fibers, mixtures thereofand the like. Preferably, the fiber surfaces are hydrophilic or aretreated to be hydrophilic. The storage layer can also include fillermaterials, such as Perlite, diatomaceous earth, Vermiculite, etc., toimprove liquid retention.

If the absorbent gelling material is dispersed non-homogeneously in acarrier, the storage layer can nevertheless be locally homogenous, i.e.have a distribution gradient in one or several directions within thedimensions of the storage layer. Nonhomogeneous distribution can alsorefer to laminates of carriers enclosing absorbent gelling materialspartially or fully.

An alternative are foam like or actual foam structures as liquidstorage. There are open cell foams which absorb liquid and throughchemical or surface interaction retain the liquid also under pressure.Such foams may be formed with a skin, thus providing on their wearerfacing surface a smooth appearance which makes the use of a topsheetoptional. Typical foams in this context are e.g. those disclosed in PCTpublications WO 93/03699, WO 93/04092, WO 93/04113.

c Optional Fibrous (“Dusting”) Layer

An optional component for inclusion in the absorbent core according tothe present invention is a fibrous layer adjacent to, and typicallyunderlying the storage layer identified by reference numeral 44 in FIG.1. This underlying fibrous layer is typically referred to as a “dusting”layer since it provides a substrate on which to deposit absorbentgelling material in the storage layer during manufacture of theabsorbent core. Indeed, in those instances where the absorbent gellingmaterial is in the form of macro structures such as fibers, sheets orstrips, this fibrous “dusting” layer need not be included. However, this“dusting” layer provides some additional fluid-handling capabilitiessuch as rapid wicking of fluid along the length of the pad.

d Other Optional Components of the Absorbent Structure

The absorbent core according to the present invention can include otheroptional components normally present in absorbent webs. For example, areinforcing scrim can be positioned within the respective layers, orbetween the respective layers, of the absorbent core. Such reinforcingscrims should be of such configuration as to not form interfacialbarriers to fluid transfer. Given the structural integrity that usuallyoccurs as a result of thermal bonding, reinforcing scrims are usuallynot required for thermally bonded absorbent structures.

Another component which can be included in the absorbent core accordingto the invention, and preferably is provided close to or as part of theprimary or secondary fluid distribution layer or the fluid storagelayer, are odor control agents such as zeolites, carbon black,silicates, EDTA or other chelates. Such agents are preferably providedin particulate form or as part of particles and can be provided togetherwith the absorbent gelling material mentioned supra.

Backsheet

The absorbent article according to the present invention also comprisesa breathable backsheet. The backsheet primarily has to prevent theextrudes absorbed and contained in the absorbent structure from wettingarticles that contact the absorbent product such as underpants, pants,pyjamas, undergarments, and shirts or jockets, thereby acting as abarrier to fluid transport. In addition however, the breathablebacksheet of the present invention permits the transfer of both watervapour and air through it and thus allows the circulation of air intoand water vapour out of the article. The backsheet typically extendsacross the whole of the absorbent structure and can extend into and formpart or all of sideflaps, side wrapping elements or wings, often presentin sanitary applications.

According to the present invention a dual or multiple layer breathablebacksheet composite is preferred in the absorbent article. According tothe present invention suitable breathable backsheets for use hereincomprise at least a first air permeable layer with apertures. Preferredbreathable multilayer backsheets for use herein are those having both ahigh vapour and high air exchange.

The first layer which is characterizing for the present invention isindicated as layer 50 in the drawings. It is positioned below thegarment facing surface of the absorbent core and the wearer facingsurface of the optional second layer which is indicated as layer 52 inFIG. 1. The first layer is oriented such that it retards or preventsliquid from passing from the absorbent core towards the outside whileallowing free air flow through it.

According to the present invention the optional second layer (52) needsto provide at least water vapour permeability so as to supportbreathability of the article. It is desirable that it also supports airpermeability in order to further improve the comfort benefit from thebreathability of the article. In this context suitable water vapour andair permeable layers include two-dimensional micro- or macro-aperturedfilms, which can also be micro-or macroscopically expanded films, formedapertured films and monolithic films, as well as nonwovens, or wovens.

Suitable 2 dimensional planar layers of the backsheet may be made of anymaterial known in the art, but are preferably manufactured from commonlyavailable polymeric materials. Suitable materials are for exampleGoretex (TM) or Sympatex (TM) type materials well known in the art fortheir application in so-called breathable clothing. Other suitablematerials include XMP-1001 of Minnesota Mining and ManufacturingCompany, St. Paul, Minn., USA and Exxaire XBF-101W, supplied by theExxon Chemical Company. As used herein the term 2 dimensional planarlayer refers to layers having a depth of less than 1 mm, preferably lessthan 0.5 mm, wherein the apertures do not protrude out of the plane ofthe layer (in contrast to so called formed films). The aperturedmaterials for use as a backsheet in the present invention may beproduced using any of the methods known in the art such as described inEPO 293 482 and the references therein. In addition the dimensions ofthe apertures produced by this method may be increased by applying aforce across the plane of the backsheet layer (i.e. stretching thelayer).

Suitable apertured formed films include films which have discreteapertures which extend beyond the horizontal plane of the garment facingsurface of the layer towards the core thereby forming protuberances. Theprotuberances have an orifice located at its terminating end. Preferablysaid protuberances are of a funnel shape, similar to those described inU.S. Pat. No. 3,929,135. The apertures located within the plane and theorifices located at the terminating end of protuberance themselves maybecircular or non circular provided the cross sectional dimension or areaof the orifice at the termination of the protuberance is smaller thanthe cross sectional dimension or area of the aperture located within thegarment facing surface of the layer. Preferably said apertured preformedfilms have a directional liquid transport and are positioned such thatthey support the prevention of liquid loss (leakage) through thebacksheet. Suitable macroscopically expanded films for use hereininclude films as described for example in U.S. Pat. Nos. 4,637,819 and4,591,523.

Suitable monolithic films include Hytrel (TM), available from DuPontCorporation, USA, and other such materials as described in Index 93Congress, Session 7A “Adding value to Nonwovens”, J-C. Cardinal and Y.Trouilhet, DuPont de Nemours international S.A, Switzerland. Suitablenon-wovens and/or wovens are any of those well known in the art.Non-wovens such as spunbonded, melt blown or carded which arethermobonded airlayed, drylayed or even wetlayed with or without binderor composites of such nonwovens in layered of mixed forms can be used.Particularly preferred non-wovens are multilayer non-wovens such as acomposite of fine melt blown fibers with more coarse spunbonded fiberswith the meltblown fibers forming the wearer facing surface of thenon-woven layer, such as those disclosed in Whitehead, U.S. Pat. No.4,578,069.

The first layer according to the present invention is preferably indirect contact with the absorbent core. It provides air and water vapourpermeability by being apertured. Preferably this layer is made inaccordance with the aforementioned U.S. Pat. No. 5,591,510 or PCT WO-97/03818, WO-97/03795. In particular, this layer comprises a polymericfilm indicated in FIG. 1 as first layer (50), having capillaries (54).The capillaries extend away from the wearer facing surface of film (50)at an angle which is less then 90 degrees. In FIGS. 2 through 4alternative embodiments of such capillaries are shown. Preferably thecapillaries are evenly distributed across the entire surface of thelayer, and are all identical. However, layers having only certainregions of the surface provided with apertures, for example only an areaoutside the region aligned with the central loading zone of theabsorbent core, maybe provided with capillaries according to the presentinvention.

Methods for making such three-dimensional polymeric films with capillaryapertures are identical or similar to those found in the apertured filmtopsheet references, the apertured formed film references and themicro-/macroscopically expended film references cited above. Typically apolymeric film such as a polyethylene (LDPE, LLDPE, MDPE, HDPE orlaminates thereof) or polypropylene (or even a water vapour permeablefilm such as those disclosed for the optional second layer) is heatedclose to its melting point and exposed through a forming screen to asuction force which pulls those areas exposed to the force into theforming apertures which are shaped such that the film is formed intothat shape and, when the suction force is high enough, the film breaksor raptures at its end thereby forming an aperture through the film.

Various forms, shapes, sizes and configurations of the capillaries arepossible and have been discussed in the art. The apertures (53) formcapillaries (54) which have side walls (56). The capillaries extend awayfrom the wearer facing surface of the film (55) for a length which is atleast such that it allows the aperture at the end of the capillaries toextend far enough away from the aperture at the opening of thecapillaries that the capillaries can collapse completely when compressedto eliminate liquid transport in the collapsed state.

The capillaries have a first opening (57) in the plane of the garmentfacing surface of the film (55) and a second opening (58) which is theopening formed when the suction force (such as a vacuum) in the abovementioned process creates the aperture. Naturally the edge of the secondopening (58) may be rugged or uneven, comprising loose elementsextending from the edge of the opening as shown in FIG. 3 and 4.However, it is preferred that the opening be as smooth as possible so asnot to create a liquid transport entanglement between the extendingelements at the end of the second opening (58) of the capillary (54)with the absorbent core (44) in the absorbent article (in contrast thismay be desirable for apertured film topsheets where such loose elementsprovide the function of sucker feet).

In one preferred embodiment according to the present invention as shownin FIG. 1 the capillaries extend “over” each other due to their angleand their length. This can be achieved when the center point of thesecond opening (as defined below) extends over or beyond of the centerpoint of an adjacent capillary.

As shown in FIG. 4 the first opening has a center point (157) and thesecond opening also has a center point (158). These center points fornon-circular openings are the area center points of the respectiveopening area. When connecting the center point (157) of the firstopening (57) with the center point (158) of the second opening (58) acenter axis (60) is defined. This center axis (60) forms an angle (59)with the plane of the film which is the same plane as the garment facingsurface of the film (55). This angle should be preferably in the rangebetween 85 and 20 degrees, more preferably between 65 degrees and 25degrees, and most preferably between 55 and 30 degrees.

It is of course possible to allow the capillaries to take the shape of afunnel such that the second opening (58) is (substantially) smaller thanthe first opening (57) when considering the opening size in a plainperpendicular to the center axis (60). Such an embodiment is shown inFIG. 3 and FIG. 2. In FIG. 2 it is also shown that the wall (56) of thecapillary may not end in the second opening (58) such that the openingforms a surface perpendicular to the center axis (60) but such that thewall on the portion of the capillary further apart from the wearerfacing surface of the film (55) extends over the opening to aid the filmin reducing the probability of liquid migrating through the capillariesfrom the absorbent core on the wearer facing side of the film (55) tothe garment facing side of the film (and cause leakage).

Without wishing to be bound by theory it is believed that thecapillaries according to the present invention in the first layer of thebreathable backsheet allow air and water vapour permeability which isnot hindered by them being slanted at an angle or by the shape asindicated above. At the same time the length slanting and shapingaccording to the present invention will enable the capillaries to closecompletely under pressure excerpted from the wearer facing side on themsuch that liquid transport through the capillaries towards the outsideof the article becomes less likely when increasing the pressure whilenot completely loosing their (air and) water vapour permeability. Hencethese three-dimensional formed film layers are highly preferable in thecontext of breathable absorbent articles and in particular so if anadditional second outer layer is provided.

According to the present invention and as defined in the appended claimsthe first layer in the slanted capillary film backsheet does provide acertain liquid water transport resistance increase when comparingambient pressure and a compression at a pressure at 6865 Pa. Thisincrease is measured with a modified DIN 53886 test. At the same timethe water vapour permeability can be measured also at ambient pressureand at the respective compression at a pressure of 6865 Pa. This watervapour permeability according to the present invention and as defined inthe appended claims is reduced by less than 80%, preferably by less than60%. Absorbent articles utilizing air and water vapour permeablebacksheets according to this invention hence have the benefit ofreducing liquid strike through problems under stress conditions i.e.when exposed to increased compression while maintaining the benefit ofbreathability under such stress conditions.

In the following the test for liquid water transport resistance and forwater vapour permeability in their modified versions are defined indetail as employed in the present invention.

Liquid Water Transport Resistance Test

The liquid water transport resistance (hereafter WTR) test is utilizedto quantify the barrier properties of a breathable backsheet materialaccording to the present invention. The test uses DIN 53866 as methodexcept where noted otherwise.

Basic Principle of the Method

The basic principle of the test is to evaluate the transport resistanceof apertured materials to distilled water. An apertured layer should besufficiently open to allow air permeability but, without the passage oflarge quantities of liquid. To ensure that this test is sufficientlyrepresentative to the situations under which different absorbentarticles are actually used distilled water is used as a representativefluid.

Method Execution

To determine the transport resistance of an apertured film a standardwater proofness tester such as Textest FX 3000 (manufactured by TexTestAG of Switzerland) water proofness tester, with a motor for continuouswater pressure increase, is used. The water pressure is applied frombelow the sample so the wearer facing side of the sample has to bedirected downwards towards the water.

In this test water pressure is measured at the moment of penetrationthrough a sample. In order to exclude random failure the pressure istaken at the time when the first droplets penetrate at a first locationand when water penetrates at a third location. Both pressure values areaveraged forming a single measurement.

The modification of this test according to the present invention is totest the respective apertured film sample without compression and undera compressive pressure. The compressive pressure is applied by placingthe sample between two plates which plates have matching apertures andcan be fixed parallel to each other.

The apertures in the plates need to be provided such that they are largeenough to present no liquid barrier but small enough to create a uniformcompression to the apertured film. This can be achieved e.g. by use ofaperture having a diameter of about 50% of the smallest diameter of theapertures in the test sample.

In FIGS. 5 and 6 a top plan view and a cross section of a sample plate(80) are shown. The total open area in a plate (80), is the sum of theareas of the apertures (61). The total open area should be as high aspossible but at least 60% of the total area of the plate.

The compressed sample preparation is done by placing the sample betweentwo plates and putting a weight on the plate which results in acompressive pressure of 6865 Pa when considering gravitational force ofthe weight divided by size of the plate including the apertures. Thisprovide a pressure between the plates relative to each other inaccordance with the compressed condition of the test. The plates arethen mechanically maintained/fixed parallel to each other (i.e.at aspacing which maintains the compression) to allow removal of the weight.

In order for the test results to be comparable the uncompressed watertransmission resistance is measured by use of a circumferencial spacingmember between two plates which spacing member has to have at least theuncompressed thickness of the apertured film.

Interpretation of Test Results

The test result for both samples compressed and uncompressed is taken asthe water pressure at the moment of water penetration through thesample. The water pressure is a linear proportional measurement of thewater transport resistance, i.e. the higher the pressure measurement isthe higher the water transport resistance of the sample is. For thecomparison of the required increase of the water transport resistanceaccording to the present invention a direct comparison of the waterpressure at the moment of penetration according to this test method isused.

In accordance with the present invention the pressure at which liquidpenetrates through the test material must be increased by at least 50%in the test using the compression relative to the test withoutcompression. For samples which have no liquid penetrating through themalready without compression the pressurized test is still necessary inorder to see whether they maintain this excellent and most desirableresult of no liquid transport through the test material. Obviously thesematerials cannot be considered according to the present invention sinceno improvement of liquid transport resistance can be achieved.

Water Vapor Permeability Test on Breathable Apertured Films

The Vapor permeability test is utilized to quantify the vaportransmission reduction of the apertured film under pressure.

Basic Principle of the Methods

The basic principle of the test is to quantify the extent of watervapour transmission of an absorbent article. The test method that isapplied is a standard one, namely ASTM E 96-80, Procedure B—Water Methodat 23° C. The test is performed in a stable temperature/humiditylaboratory maintained at a temperature of 23° C. at 50% RH, allmaterials are conditioned at the laboratory conditions for a period of24 hours. The vapor permeability value is determined as the weight lossin g divided by the open area of the sample holder in m² and quoted perday; i.e.:

Vapor Permeability=Weight Loss (g)/open area (m²)/24 (hrs)

Modified Water Vapor Permeability Test

The modified test uses the same procedure as the basic water vaporpermeability test including the respective test stand but placed on topof the side of the test material which is designated to be facing theabsorbent core. In order to allow this the test also needs to bemodified in that a standard absorbent structure is placed on that sideof the film which is facing the absorbent core in an absorbent article.The standard absorbent structure in loaded with a sufficient quantity ofwater to ensure complete liquid water availability on the “inside” sideof the test material. The cup of the ASTM test does then also not needto be filled with water any more.

The standard absorbent structure is composed of 4 layers (folded as astack) of airlayed tissue of 63 g/m² basis weight {available fromWalkisoft, USA under the supplier code Metmar(P50W.IPED)} havingdimensions of 20 cm×6.5 cm. The test material which has the samedimensions is then placed on the bottom side of this structure withoutany additional adhesive attachment. Then a compressive load of 70 g/cm²(equivalent to 6865 Pa) is placed to the construction. This can be donewith an apertured plate as used in the WTR test or similar. Forcomparison the open area has to be reconsidered in light of the reducedsurface available for water vapor permeability when using an aperturedplate. Alternatively to allow a direct comparison the plate can be usedfor the test with or without compressive pressure.

According to the present invention a test material which hassuccessfully qualified under the water transport resistance test thenhas to maintain at least 80% of its water vapor permeability to fallwithin the present invention.

Air Permeability Test

The air permeability test is utilized to assess the ability of anabsorbent structure to circulation/exchange air.

Basic Principle of the Methods

The basic principle of the test is to evaluate the resistance of anabsorbent article to the passage of air. In this test, the volume (oramount) of air that flows through an article of given dimensions understandard conditions (of 23° C./50% RH) is measured. The instrumentutilized for the test is: Air Permeabilimeter FX 3300 manufactured byTexTest AG Switzerland.

Samples should be allowed to equilibrate in the test environment for atleast 4 hrs prior to commencement of the measurement. The article(having dimensions exceeding 5 cm² the dimensions of the measurementhead) is placed on the device to measure the volume of air flow at apressure drop of 1210 Pa that sucks air through the sample layer orstructure. The device measures the volume of air flow and the pressuredrop across the orifices that contains the sample and measurement head.Finally the device generates a value of air permeability in the units ofliters/m²/s.

Preferred articles according to the present invention have an airpermeability in dry conditions without compressive pressure of not lessthan 1000 liter /m²/s according to this test.

Absorbent Article Construction

According to the present invention the absorbent article can be usedbeneficially in the context of sanitary napkins, panty liners,incontinence articles, sweatpads, breast pads and diapers. However,sanitary napkins are particularly susceptible to the present invention.The disposable article may thus also have all those features and partswhich are typical for products in the context of their intended use.

What is claimed is:
 1. Breathable disposable absorbent article oflayered construction, each layer or system of layers having a garmentfacing surface, which is oriented to face in the direction of a garment(21) during use of the article, and a wearer facing surface, which isoriented to face in the direction of the wearer (20) during use of thearticle, said article comprising at least an absorbent core (40, 42,44); a breathable backsheet (50, 52) located on said garment facingsurface of said absorbent core (40, 42, 44), said backsheet (50, 52)comprising at least a first backsheet layer (50) said first backsheetlayers (50) being water vapor permeable, said first backsheet layer (50)comprising a resilient, three dimensional web, said web consists of aliquid impervious polymeric film (55) having apertures (53), saidapertures (53) forming capillaries (54), said capillaries (54) havingside walls (56) which extend away from said wearer facing surface ofsaid film (55), said capillaries (54) having a first opening (57) insaid garment facing surface of said film (55) and a second opening (58)at the end of said capillaries (54) spaced apart from said wearer facingsurface of said film (55), said web has a liquid water transportresistance (WTR) in a direction from said second opening (58) towardssaid first opening (57) of said capillaries (54) measured by a modifiedDIN53886 test for WTR and said web has a water vapour permeability (WVP)in a direction from said second opening (58) towards said first opening(57) measured by a modified ASTM E 96-80 test for WVT of saidcapillaries (54), said article being characterized in that said WTR ofsaid web increases at least 50% and said WVP reduces less than 80% whencomparing WTR and WVP at ambient pressure with a compression of 6865 Paabove ambient pressure.
 2. Breathable disposable absorbent articleaccording to claim 1 characterized in that said capillaries (54) extendaway from said wearer facing surface of said film (55) at an angle (59)of less than 90° measured from the plain of said film.
 3. Breathabledisposable article according to claim 1 characterized in that saidcapillaries (54) are all substantially identical, preferably saidcapillaries (54) are homogeneously distributed across said film (55) ata spacing which ensures the WVP reduces less than 80%, when comparingthe values at ambient pressure 6865 Pa.
 4. Breathable disposable articleaccording to claim 1 characterized in that said WTR of said webincreases at lest 65%, when comparing the values at ambient with acompression of 6865 Pa.
 5. Breathable disposable article according toclaim 1 characterized in that said first opening (57) of each of saidcapillaries (54) has a center point (157) and said second opening ofeach of said capillaries also has a center point (158) and a lineconnecting said center points defines a center axis (60) of each of saidcapillaries (54), said center axis (60) forming an angle (59) with theplane of said film (55), said angle being between 55° and 30°. 6.Breathable disposable article according to claim 1 claims characterizedin that at least some of said capillaries form cones having liquidtransport areas which are reducing in a direction areas towards theabsorbent core (40, 42, 44) when comparing areas perpendicular to saidcenter axis (60).
 7. Breathable disposable article according to claim 1characterized in that said capillaries (54) are curved towards saidplane of said film.